The goal of the proposed research is to develop a highly sensitive and specific radioimmunoassay for platelet activating factor (PAF). PAF is a lipid mediator produced by a variety of inflammatory cells such as neutrophils, platelets, macrophages, eosinophils, and vascular endothelial cells. PAF induces a number of in vivo effects including acute bronchoconstriction and bronchopulmonary hyperreactivity accompanied by platelet, eosinophil, and macrophage activation and recruitment. Thus the role of PAF In the pathophysiology of immediate hypersensitivity reaction (especially asthma) and inflammation is apparent. Specific aims include: 1) preparation of a metabolically stable PAF derivative suitably functionalized for protein conjugation, 2) preparation of a PAF-protein conjugate, 3) production of antibodies to the conjugate by immunization of rabbits, 4) production of PAF radioimmunoassay kits for commercialization. A large number of pharmaceutical companies are developing novel and more specific therapeutic agents based on PAF inhibition or antagonism and these kits are expected to find wide application.